title: Retention force of T-bar clasps for titanium and cobalt-chromium removable partial dentures.
abstract: The objective of this study was to evaluate the retention force of T-bar clasps made from commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) alloy by the insertion/removal test simulating 5 years use. Thirty-six frameworks were cast from CP Ti (n=18) and Co-Cr alloy (n=18) with identical prefabricated patterns on refractory casts from a distal extension mandibular hemi-arch segment. The castings were made on a vacuum-pressure machine, under vacuum and argon atmosphere. Each group was subdivided in three, corresponding to 0.25 mm, 0.50 mm and 0.75 mm undercuts, respectively. No polishing procedures were performed to ensure uniformity. The specimens were subjected to an insertion/removal test and data was analyzed statistically to compare CP Ti and Co-Cr alloy in the same undercut (Student's t-test for independent samples) and each material in different undercuts (one-way ANOVA) (p=0.05). Comparisons between materials revealed significant differences (p=0.017) only for the 0.50-mm undercut. No significant differences (p>0.05) were found when comparing the same material for the undercuts. It may be concluded that for different undercuts, both Co-Cr alloy and CP Ti had no significant differences for T-bar clasps; CP Ti showed the lowest retention force values when compared to Co-Cr alloy in each undercut, but with significant difference only for the 0.50-mm undercut; and both materials maintained the retentive capacity during the simulation test.
authors.affiliation: Department of Dental Materials and Prosthodontics, Dental School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil. renata@forp.usp.br
authors.forename: Renata Cristina Silveira
authors.initials: RC
authors.lastname: Rodrigues
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Macedo
authors.forename: Erica Miranda
authors.initials: EM
authors.lastname: de Torres
authors.forename: Maria da Glória Chiarello
authors.initials: Mda G
authors.lastname: de Mattos
authors.forename: Ricardo Faria
authors.initials: RF
authors.lastname: Ribeiro
mesh_terms: D001128:Argon / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry*; D016734:Dental Clasps; D003764:Dental Materials / Q000737:chemistry*; D003775:Dental Polishing; D003779:Denture Design; D003781:Denture Retention; D003832:Denture, Partial, Removable; D006801:Humans; D008422:Materials Testing; D011312:Pressure; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D014618:Vacuum
chemical_list: D002858:Chromium Alloys; D003764:Dental Materials; D001128:Argon; D014025:Titanium